Olfactory regulation of sex pheromone production in the lady beetle Harmonia axyridis

Female Asian lady beetle, Harmonia axyridis (Coleoptera: Coccinellidae), exhibit a stereotyped calling behavior associated with the release of a volatile blend mainly composed of five terpenoid compounds, which attracts males and triggers copulation. The release of this sex pheromone occurs only in the presence of aphid prey. This study aims to (1) identify the olfactory cues that trigger sex pheromone production in H. axyridis and (2) evaluate the impact of larval diet quality and quantity on adult pheromone release. Using dynamic sampling of volatile organic compounds (VOCs) followed by thermal desorption gas chromatography (TD-GC-MS/FID), we demonstrate that exposure to aphid- emitted VOCs alone is sufficient to induce sex pheromone production in H. axyridis females. To further identify the specific cues involved, females were either exposed to aphid alarm pheromone or aphid honeydew, known for being composed of multiple bacteria-born VOCs. This experiment is currently underway. In addition, variations in larval diet quality and quantity did not significantly affect adult pheromone production, highlighting the predominant role of aphid-derived cues perceived during adulthood. Overall, our results emphasize the importance of prey-associated olfactory signals in regulating sexual communication in H. axyridis and provide new insights into the ecological factors shaping pheromone-mediated mating interactions in predatory insects.